As a postdoc at Montana State University in 2015/2016 with Carl Yeoman’s lab, I consulted on a project led by then-PhD student Lola Betiku on a metagenomics dataset from two locations from the digestive tract of trout. Lola is now an Assistant Professor at Florida A&M University, and has been kind enough to continue working on this project to get it published. It was just accepted in the journal Aquaculture Reports!

Citation

Betiku, O., Yeoman, C., Gaylord, T.G., Ishaq, S., Duff, G., Sealey, W. 2023. Evidence of a Divided Nutritive Function in The Rainbow Trout (Oncorhynchus mykiss) Mid- and Hind-Gut Microbiomes by Whole Shotgun Metagenomic Approach. Aquaculture Reports 30: 101601.

Highlights

• •Animal and plant protein diets were fed to rainbow trout in a commercial setting.
• •Shotgun metagenomic analysis of the mid-GIT and hind-GIT was carried out.
• •Diets influenced microbial compositions in the two GIT sections.
• •Animal protein-based diet provided metabolites for microbial protein fermentation.
• •Plant-based diet enhanced amino acid catabolism in the mid-GIT section.

Abstract

The nutritive role and ecology of gut-dwelling microbes in rainbow trout remain enigmatic. To improve our understanding of the rainbow trout gastrointestinal tract (GIT) microbiome, we performed whole shotgun metagenomic analyses on the assembled contigs from luminal contents from both mid- and hind-GIT regions for taxonomic and functional classifications of fish-fed animal and plant protein dietary sources. Our study revealed that trout respond well to the two diets containing animal and plant protein sources when supplemented with essential amino acids to meet the requirements of the fish. Microbes present were predominantly bacteria (89.9%) and mainly of the phyla Tenericutes, Firmicutes, Fusobacteria, and Proteobacteria. Eukaryotic (8.8%) microbes were mainly from phyla Ascomycota and Basidiomycota, while Archaea (<1%) were also present and predominantly from the phylum Euryarchaeota. Comparisons of genus-level classifications and functional profiles revealed compositional differences in these GIT locations that appear modulated by differences in the dietary treatments. The functional analysis provided evidence of amino acid biosynthesis/catabolism and methane production in the mid-GIT, while in the hind-GIT, proteolytic hydrolysis and butyrate metabolism were expressed in the trout fed with plant protein diet. The animal protein-based diet provided metabolites for microbial protein fermentation in the hind-GIT. Our report highlights and identifies the potential nutritive contributions of GIT microbes to trout and a potentially crucial functional division along the GIT. Finally, the plant-based diet enhanced amino acid catabolism in the midgut section, while the hindgut section supports evidence of methanogen fermentation.